The invention relates to ophthalmic lenses. In particular, the invention provides lenses that use more than one optical power, or focal length, and are useful in the correction of presbyopia.
As an individual ages, the eye is less able to accommodate, or bend the natural lens, to focus on objects that are relatively near to the observer. This condition is known as presbyopia. Additionally, for persons who have had their natural lens removed and an intraocular lens inserted as a replacement, the ability to accommodate is totally absent.
Among the methods used to correct for the eye""s failure to accommodate is the mono-vision system in which a person is fitted with one contact lens for distance vision and one lens for near vision. The mono-vision system permits the lens wearer to distinguish both distance and near objects, but is disadvantageous in that a substantial loss in depth perception results.
In another type of multifocal contact lenses, the optic zone of each lens is provided with more than one power. For example, the optic zone may have both distance and near power, which the eye uses simultaneously.
Neither of these methods provides good results in terms of visual acuity and lens wearer satisfaction. Thus, a need exists for lenses that both provide correction for the wearer""s inability to accommodate and that overcome some or all of the disadvantages of known lenses.